Carlsen takes the chance to modify the pawn structure to \"hanging pawns.\" From the isolani family, this is considered the most beneficial relative.
16... a6d3  17. e2d3  17... b8c8 The opening is a success for Black. He has managed to trade a pair of minor pieces—always a good thing in the ensuing battle with the isolated/hanging pair of pawns. 18. e1g1  18... e8g8 